Adsorption of polar components from ternary mixtures on porous silica gels

An Experimental Study on Production of Silica Aero-Gel Using Fly Ash from Coal-Fired Power Plants

silica aero-gels were synthesized from coal fly ash at ambient pressure. The experimental procedure for silica aero-gels production included alkali dissolution of fly ash, surface hydrophobic treatment of the wet-gel, followed by drying of the wet-gel samples at ambient pressure wasinvestigated. Optimized experimental parameters for production of silica aero-gels from fly ash were obtained through systematic studies. BET, SEM and FTIR and contact angle measurement were used in order to investigate the structure and characteristics of the silica aero-gel powders.

Liquid adsorption of n-octane/octanol/ethanol on SBA-16 silica

SBA-16 silica samples with cubic Im3 m symmetry were synthesized according to methods reported in literature and characterized by nitrogen adsorption and X-ray diffraction. The adsorption behavior of the n-octane(1)/octanol(2), n-octane(1)/ethanol(3), and octanol(2)/ethanol(3) binary liquid mixtures on SBA-16 was studied over the whole concentration range at 25 degrees C. Inverted U-shape isotherms were found and described by mathematical functions. The experimental binary data were verified by using a consistency test for the specific free wetting energies on the liquid/solid interface. The ternary adsorption excess isotherms of n-octane(1)/octanol(2)/ethanol(3) at 25 degrees C were predicted from the binary data. The work presents the first complete and consistent tabular set of binary liquid adsorption data for creating ternary data on ordered mesoporous silica.

Calculation of immersion enthalpy data from adsorption isotherms

The thermodynamic equations for the calculation of binary and ternary immersion data in excess formalism are presented. Immersion enthalpies and entropies of the n-hexane/n-octane, n-octane/n-tetradecane and n-hexane/n-tetradecane binary mixtures as well as the n-hexane/n-octane/n-tetradecane ternary mixture on activated carbon are calculated from the temperature dependence of adsorption isotherms. In order to evaluate the quality of the calculations, the calculated immersion enthalpies of the binary mixtures on activated carbon are compared with those that were measured calorimetrically. It is shown that phenomenological thermodynamics can be used successfully to predict calorimetric data on the basis of adsorption excess isotherms.

Prediction of multicomponent liquid adsorption using excess quantities

The utilization of excess quantities as the basis for a thermodynamic approach can simplify the prediction of multicomponent liquid adsorption from binary data. A new method for predicting liquid adsorption on solids is suggested, which is different from the existing equations with respect to the theoretical background and formulation. The applicability of the new model is tested with three ternary adsorption systems. The predicted surface excesses are discussed and compared with experimental ones and with those of other prediction models in the literature. The accordance between measured and predicted ternary data is convincing.

Prediction of multicomponent liquid adsorption using excess quantities

The utilization of excess quantities as the basis of a thermodynamic approach can simplify the prediction of multicomponent data from binary ones. Whereas in Part II the excess formalism was applied to the prediction of liquid phase adsorption on solids, in this paper, the liquid/air interface is investigated. In order to show the generality of the suggested approach, thermodynamic equations are developed in analogy to Part II. Surface tensions are predicted by different excess models and compared with experimental data. From predicted surface tensions, ternary adsorption isotherms on the liquid/air interface are calculated.

Calculation and Prediction of Adsorption Excesses on the Ternary Liquid Mixture/Air Interface from Surface Tension Measurements

The surface tensions of the n-propanol/ethylene glycol/water ternary mixture and its binary mixtures are measured at 293 K and described by mathematical functions. The experimental data and their descriptions are shown in the three-dimensional space by means of coordinate transformation. A thermodynamic model to calculate and predict ternary adsorption excess data on the ternary liquid mixture/air interface from surface tensions is presented. The calculated adsorption excess data in the ternary triangle are discussed.

Binary and Ternary Adsorption of n-Alkane Mixtures on Activated Carbon

The adsorption isotherms of the binary n-alkane mixtures n-hexane/n-octane, n-octane/n-tetradecane, and n-hexane/n-tetradecane on the activated carbon TA 95 are measured at 298 K and described with mathematical functions. About 40 experimental values of the adsorption excess of the ternary mixture n-hexane/n-octane/n-tetradecane on activated carbon TA 95 at 298 K are gas chromatographically measured inside the ternary triangle. The ternary data are represented in the three-dimensional space with the help of transformation of coordinates and by utilization of the conception of the quasi-two-component representation of the mole fractions. A consistency test for the specific wetting Gibbs energies calculated from the binary data is carried out. The possibilities for a mathematical prediction of ternary data from adsorption data for the constituent binary mixtures are proved. Copyright 1999 Academic Press.